Do they though? Don't think I ever met someone who worries about that.

Well, if you believe in an etternal afterlife you might possibly be around for that long, but I think any kind of afterlife would exist on a different plain from the universe as we know it.

Hi kayleigh,

Toretorden gave a good description of how we are, each of us, a community of cells that grow as they do by following the instructions that are their DNA molecules, with the environment having some impact on how the instructions are used.

My interest in life and how it works inspired me to study biology. You get a feeling for "how humans (living organisms) actually work" by studying general biology, anatomy, cell biology, and biochemistry, and then chemistry and physics. Usually students start with biology, then take physics, then chemistry, but may not get to really feel or see how the information combines to give a deeper understanding of how life works until they get to biochemistry (and enzymology). I feel biochemistry, the chemistry of life, really shows best on a fundamental level how our bodies use food energy to keep themselves and their processes going.

I get really excited about the topic of how we work! For example, do you recall that inside your cells are small oval structures, the mitochondria, which allow your cells to transfer some of the energy of food into the energy of a type of molecule (ATP) that cells use to drive cell processes? This process requires oxygen, and is essentially like a controlled fire. When you mix wood, oxygen, and a spark, you get fire. In us, the food that we eat is what gets "burned," but the body doesn't release all the energy as heat. Instead, a lot of the energy is bound up as chemical energy...the energy that is in the bonds holding one atom to another.

Also, something else fascinating is that our cells have mitochondria because long ago one of our (free-living) ancestor cells engulfed (but did not digest) a free-living bacterium, according to the theory of endosymbiosis (which is accepted as fact because of all the evidence).

So, we humans (and other animals) are like a slow, controlled burning fire...and we are partly bacterial in origin! Weird and wonderful.

I love the way we living beings are like one gigantic organism that stretches through time, like a growing vine, where only the tips of the branches remain alive. Each of us feels like a separate being, but in fact is actually just the present-time manifestation of this giant organism (life) that began billions of years ago.

I don't worry about what will happen to the universe far in the future...but I definitely think about it. Learning about what science predicts gives me a sense of perspective...and a sense of sadness for those organisms who will probably evolve on other planets far in the future and, due to the universe's expansion, will not be able to see and learn as much about the universe and its origins as humans can now.

Another biology student, yey! Some good classic analogies used above. Can't beat a few good analogies to get across a potentially complicated concept. I think the key to a good understanding of something complex is to be able to make it understandable to a wider audience. Guess that's why people like Dawkins and Hawkings are so successful as popular (to an extent) fiction writers.

i understand the structure of DNA etc, as when i dont Biology, it was the sections which included humans in which i was most interested in. as i wanted to know how and why everything in a human works, but what starts it all off? is the mother/baby relationship basically like jumpstarting a car?
anyways thanks Tore, that decribed some stuff i actually found confusing and difficult at school :D.

i can relate to that in bold! thats why i want to study Biology :D.
the italics i found was a good metaphor to describe the way in which the body works, thanks.
i found the rest helpful also, thanks Veg! :)

Just to nitpick, A (adenine) is complementary to T (thymine) and G (guanine) is complementary to C (cytosine). Triplets of these also code for amino acids, which in turn generate chains of protein with specific structures related to their function. Just to elaborate.

:)

Hello kayleigh, I would say that with humans it begins with sex :)and that a new individual forming is more like an avalanche than jumpstarting a car. Once an egg and sperm cell...both individual, free-living cells...unite to form a single cell (kind of like the reverse of eating!), the cell divides to form two cells, and each of those divide, and so on and so on....like a tumor, but with organized structures. I view there as being no "beginning" of a human because the egg and sperm that united to become what would grow into me were also "me" in the sense that they were alive and I continue their life. Many embryos (perhaps 1/3rd, I recall reading) have defects causing them to die before a person even realizes she is pregnant. When you ask about how a human works, do you mean you are interested in how all the embryonic cells divide and move around to create the different parts of a baby human?

Oh, good catch, dollarsandcents! I just sort of bleeped right over whether the fake DNA sequence correctly used complementary nucleotides on annealing strands!

no its not that, ive learned all that :p:, its what drives the body to actually work. what is there, that makes the body does what it does, its hard to explain, once i find the right words i will come back cos its crossing wires right now :(

show off! im surprised you never mentioned the replacement of Thymine by Uracil in RNA :).

The central dogma, duh!

;)

What? I know that of course. How could I get that wrong? Embarassing :confused:

Hm, it is quite hard to understand what you are asking.

Let's try something different. In nature, you can have evolution. Put a bit simply, it's something that happens when you have things which can replicate, can change (for better or worse) and compete for resources. Organisms are not the only things which can be said to evolve. As an example, fashion can evolve. The fashion ideas can replicate in that they can spread from person to person, they can change and give rise to modified or new ideas and there are only so many customers to buy them. Customers are a bit choosy, so some clothes made from certain ideas will sell better than others and vice versa. Some fashion ideas will die out while others live on and change into new ideas in the future.

The basic common scientific hypothesis for how life started is that early on, what would become life were molecules, nucleic acids like DNA and/or RNA, that were able to change like they do today by mutation. They could also replicate, but this required resources that they were competing for. Maybe they existed only in the tiniest cracks, the tiniest spaces where the chemical processes on which they were dependent on were protected enough for it to work. Quite possibly, replication in the early phase wasn't easy and would often yield mutated, broken copies. Mutation outside of replication could also be dangerous. However, on rare occasions one would change in a way that it improved or gained a new ability that overall made it a bit more succesful at replicating itself than the others - for example a chemical process included in getting resources was made more stable. The most successful would produce more copies and would more often pass those good qualities on to their offspring. Although you probably wouldn't consider them to be "alive" at the earliest stage, they were evolving - improving and gaining abilities over generations.

There could be different strategies, some could work together, some could perhaps utilize more aggressive tactics and destroy others, some could perhaps parasitize others. Let's not get swamped with details, though - the point is that when something like this starts evolving, you get a rise order and complexity. It's simply a matter of cause and consequence. Eventually, over countless generations, one of these proto-lineages evolved into us and a multitude of other organisms (okay, we got bits of viral/prokaryote DNA as well and there are horizontal gene transfer events in life's history and so on, but to keep it simple).

I don't think you're asking for an explanation on evolution or how life came around, but important from early on were certain chemical processes on which proto-life depended upon. Without such processes, they would not be able to replicate. As Erica wrote, your own life comes from your parents life which came from their parents life again. There's a "living" unbroken chain of these chemical processes going on in your ancestors down to the very earliest proto-life of your earliest ancestors. As Erica wrote, humans are not so much starts as they are continuations. If you wanna know where your "life processes" really started, you have to dig very deep indeed - back to life's start.

I hope that gives just a slight bit more insight!

edit :

Hah, skimming over it I see I've basically repeated some of the points already made and a point I myself tried to make in my first answer. Oh well, if this doesn't answer your question, perhaps it narrows it down a bit. ;)